When sameFormFieldsAsArray is set to true, when all fields with the same name are empty, it's not converted to an array of empty strings (as expected). If only one of the fields is filled out, it's passed as a string, and the other empty strings are not passed as elements in an array. This broke portions of our application that had previously been working on 5.3.2+77.
It seems the fix that was added to correct didn't account for empty fields.
Updated the repro from the earlier issue to demonstrate: https://github.com/mjclemente/lucee-error-sameFormFieldsAsArray